Readers respond to previous issues

Regarding the article about Professor Ruddiman [“Humans began changing climate 7,000 years ago,” UVA News, October 6], I pose the following query: What vehicles, factory smokestacks, home furnaces, etc. did the population possess 5,000 years ago generating CO2? Also, is the current melting of the Martian icecaps due to the Martians riding around in their […]